OEM views meeting   12/03/96   - Yue
Attendees: Serge, Jason, Roy, Vasilis, Janet, Yue, Hector.

We discussed OEM view specification. We did not reach any agreement yet, 
but we come up with the following issues. 

Assume we are defining an OEM view on top of an OEM database.

-- filtering : specifying a view is to decide which nodes/edges from
the base DB to keep and hide.

-- virtual names/entry points to view objects: they can be specified
by one or more LOREL queries.

-- virtual objects and values: adding new nodes and edges to a view. 

-- classification: view mechanism can be used to classify OEM objects
according to their value or structure.  

-- multiple roles of an object: the same object could appear in both
base DB and in one or more views. Attributes of such an object 
(e.g., its children) as well as relationships between this object 
and others (e.g., edges) may appear in one database but not in another. 
As a result, the same query MAY return different answers depending 
on whether the query is sent to the base DB or to the view.


We then further discussed alternatives to specify an OEM view:

1. specify desired objects and implicitly keep all edges among the
selected objects.

2. specify desired edges and implicitly keep all nodes related to
selected edges.

3. explicitly specify both nodes and edges that appear in a view.

For the next time, Jason and Vasilis may come up with more detailed
examples using the above approaches.  Related, we want to consider
scenarios that a view may be used. A few of those scenarios are:
compute a view, answer a query on a view, add new information to a
view, materialize and maintain a view.